Identification of different gene expressions between diffuse- and intestinal-type spheroid-forming gastric cancer cells.

BACKGROUND: Three-dimensional in vitro spheroid models are unique because they are considered for enrichment of specific cell populations with self-renewal ability. In this study, we explored the different mechanisms of gastric cancer spheroid-forming cells according to the Lauren classification. METHODS: We isolated and enriched cells with self-renewal ability using spheroid-forming methods from gastric cancer cell lines. The expression of candidate target genes was investigated using western blot and qRT-PCR analysis. Lentiviral shRNA knockdown of target gene expression was performed and the effects on spheroid, colony forming, and tumorigenic ability were analyzed. RESULTS: The SNU-638, SNU-484, MKN-28, and NCI-N87 successfully formed spheroid from single cell and enriched for self-renewal ability from 11 gastric cancer cell lines, including diffuse and intestinal types. The expression of SOX2 and E-cadherin increased in spheroid-forming cells in a diffuse-type cell line (SNU-638 and SNU-484), but not in the intestinal type (MKN-28 and NCI-N87). In contrast, ERBB3 expression was only increased in intestinal-type spheroid cells. The depletion of each candidate target gene expression suppressed self-renewal ability to grow as spheroids and colonies in a soft agar assay. In particular, down-regulated ERBB3 in the intestinal-type cell lines inhibited tumor growth in a mouse xenograft model. We found that high ERBB3 gene expression correlates with decreased survival in the intestinal type of gastric cancer. CONCLUSIONS: Our results suggest that diffuse- and intestinal-type spheroid-forming cells express genes differently. Our data suggest that these candidate genes from spheroid-forming cells can be used in applications in targeted therapy.

Genetic variants associated with longer telomere length are associated with increased lung cancer risk among never-smoking women in Asia: a report from the female lung cancer consortium in Asia.

Recent evidence from several relatively small nested case-control studies in prospective cohorts shows an association between longer telomere length measured phenotypically in peripheral white blood cell (WBC) DNA and increased lung cancer risk. We sought to further explore this relationship by examining a panel of seven telomere-length associated genetic variants in a large study of 5,457 never-smoking female Asian lung cancer cases and 4,493 never-smoking female Asian controls using data from a previously reported genome-wide association study. Using a group of 1,536 individuals with phenotypically measured telomere length in WBCs in the prospective Shanghai Women's Health study, we demonstrated the utility of a genetic risk score (GRS) of seven telomere-length associated variants to predict telomere length in an Asian population. We then found that GRSs used as instrumental variables to predict longer telomere length were associated with increased lung cancer risk (OR = 1.51 (95% CI = 1.34-1.69) for upper vs. lower quartile of the weighted GRS, p value = 4.54 × 10(-14) ) even after removing rs2736100 (p value = 4.81 × 10(-3) ), a SNP in the TERT locus robustly associated with lung cancer risk in prior association studies. Stratified analyses suggested the effect of the telomere-associated GRS is strongest among younger individuals. We found no difference in GRS effect between adenocarcinoma and squamous cell subtypes. Our results indicate that a genetic background that favors longer telomere length may increase lung cancer risk, which is consistent with earlier prospective studies relating longer telomere length with increased lung cancer risk.

Genome-wide association study of lung cancer in Korean non-smoking women.

Lung cancer in never-smokers ranks as the seventh most common cause of cancer death worldwide, and the incidence of lung cancer in non-smoking Korean women appears to be steadily increasing. To identify the effect of genetic polymorphisms on lung cancer risk in non-smoking Korean women, we conducted a genome-wide association study of Korean female non-smokers with lung cancer. We analyzed 440,794 genotype data of 285 cases and 1,455 controls, and nineteen SNPs were associated with lung cancer development (P < 0.001). For external validation, nineteen SNPs were replicated in another sample set composed of 293 cases and 495 controls, and only rs10187911 on 2p16.3 was significantly associated with lung cancer development (dominant model, OR of TG or GG, 1.58, P = 0.025). We confirmed this SNP again in another replication set composed of 546 cases and 744 controls (recessive model, OR of GG, 1.32, P = 0.027). OR and P value in combined set were 1.37 and < 0.001 in additive model, 1.51 and < 0.001 in dominant model, and 1.54 and < 0.001 in recessive model. The effect of this SNP was found to be consistent only in adenocarcinoma patients (1.36 and < 0.001 in additive model, 1.49 and < 0.001 in dominant model, and 1.54 and < 0.001 in recessive model). Furthermore, after imputation with HapMap data, we found regional significance near rs10187911, and five SNPs showed P value less than that of rs10187911 (rs12478012, rs4377361, rs13005521, rs12475464, and rs7564130). Therefore, we concluded that a region on chromosome 2 is significantly associated with lung cancer risk in Korean non-smoking women.

Genetic Characteristics Associated With Drug Resistance in Lung Cancer and Colorectal Cancer Using Whole Exome Sequencing of Cell-Free DNA.

Circulating cell-free DNA (cfDNA) can be used to characterize tumor genomes through next-generation sequencing (NGS)-based approaches. We aim to identify novel genetic alterations associated with drug resistance in lung cancer and colorectal cancer patients who were treated with EGFR-targeted therapy and cytotoxic chemotherapy through whole exome sequencing (WES) of cfDNA. A cohort of 18 lung cancer patients was treated with EGFR TKI or cytotoxic chemotherapy, and a cohort of 37 colorectal cancer patients was treated with EGFR monoclonal antibody or cytotoxic chemotherapy alone. Serum samples were drawn before and after development of drug resistance, and the genetic mutational profile was analyzed with WES data. For 110 paired cfDNA and matched germline DNA WES samples, mean coverage of 138x (range, 52-208.4x) and 47x (range, 30.5-125.1x) was achieved, respectively. After excluding synonymous variants, mutants identified in more than two patients at the time of acquired resistance were selected. Seven genes in lung cancer and 16 genes in colorectal cancer were found, namely, APC, TP53, KRAS, SMAD4, and EGFR. In addition, the GPR155 I357S mutation in lung cancer and ADAMTS20 S1597P and TTN R7415H mutations in colorectal cancer were frequently detected at the time of acquired resistance, indicating that these mutations have an important function in acquired resistance to chemotherapy. Our data suggest that novel genetic variants associated with drug resistance can be identified using cfDNA WES. Further validation is necessary, but these candidate genes are promising therapeutic targets for overcoming drug resistance in lung cancer and colorectal cancer.

Genomic Landscape and Clinical Utility in Korean Advanced Pan-Cancer Patients from Prospective Clinical Sequencing: K-MASTER Program.

The fundamental principle of precision oncology is centralized on the identification of therapeutically exploitable targets that provides individual patients with cancer an opportunity to make informed decisions on a personalized level. To facilitate and adopt such concepts within clinical practice, we have initiated a nationwide, multi-institutional precision oncology screening program to examine and enroll patients into the most appropriate clinical trial based on their tumor's unique molecular properties. To determine the prevalence of essential major driver mutations and to explore their dynamic associations at both molecular and pathway levels, we present a comprehensive overview on the genomic properties of East Asian patients with cancer. We further delineate the extent of genomic diversity as well as clinical actionability in patients from Western and Eastern cultures at the pan-cancer and single-tumor entity levels. To support fellow oncology communities in future investigations involving large-scale analysis, all data have been made accessible to the public (https://kmportal.or.kr). SIGNIFICANCE: We present a comprehensive overview of molecular properties of East Asian pan-cancer patients and demonstrate significant diversity in terms of genomic characteristics as well as clinical utility compared with patients with European ancestry. The results of this study will lay the groundwork for designing personalized treatments in the clinical setting. See related commentary by Moyers and Subbiah, p. 886. This article is highlighted in the In This Issue feature, p. 873.

Comparison of the Data of a Next-Generation Sequencing Panel from K-MASTER Project with That of Orthogonal Methods for Detecting Targetable Genetic Alterations.

PURPOSE: K-MASTER project is a Korean national precision medicine platform that screened actionable mutations by analyzing next-generation sequencing (NGS) of solid tumor patients. We compared gene analyses between NGS panel from the K-MASTER project and orthogonal methods. MATERIALS AND METHODS: Colorectal, breast, non-small cell lung, and gastric cancer patients were included. We compared NGS results from K-MASTER projects with those of non-NGS orthogonal methods (KRAS, NRAS, and BRAF mutations in colorectal cancer [CRC]; epidermal growth factor receptor [EGFR], anaplastic lymphoma kinase [ALK] fusion, and reactive oxygen species 1 [ROS1] fusion in non-small cell lung cancer [NSCLC], and Erb-B2 receptor tyrosine kinase 2 (ERBB2) positivity in breast and gastric cancers). RESULTS: In the CRC cohort (n=225), the sensitivity and specificity of NGS were 87.4% and 79.3% (KRAS); 88.9% and 98.9% (NRAS); and 77.8% and 100.0% (BRAF), respectively. In the NSCLC cohort (n=109), the sensitivity and specificity of NGS for EGFR were 86.2% and 97.5%, respectively. The concordance rate for ALK fusion was 100%, but ROS1 fusion was positive in only one of three cases that were positive in orthogonal tests. In the breast cancer cohort (n=260), ERBB2 amplification was detected in 45 by NGS. Compared with orthogonal methods that integrated immunohistochemistry and in situ hybridization, sensitivity and specificity were 53.7% and 99.4%, respectively. In the gastric cancer cohort (n=64), ERBB2 amplification was detected in six by NGS. Compared with orthogonal methods, sensitivity and specificity were 62.5% and 98.2%, respectively. CONCLUSION: The results of the K-MASTER NGS panel and orthogonal methods showed a different degree of agreement for each genetic alteration, but generally showed a high agreement rate.

Clathrin-mediated EGFR endocytosis as a potential therapeutic strategy for overcoming primary resistance of EGFR TKI in wild-type EGFR non-small cell lung cancer.

OBJECTIVES: Oncogenic alterations of epidermal growth factor receptor (EGFR) signaling are frequently noted in non-small cell lung cancer (NSCLC). In recent decades, EGFR tyrosine kinase inhibitors (TKIs) have been developed, although the therapeutic efficacy of these inhibitor is restricted to EGFR-mutant patients. In this study, we investigated that clathrin-mediated EGFR endocytosis hampers the effects of gefitinib and sustains NSCLC cells with wild-type EGFR. MATERIALS AND METHODS: NSCLC cell lines (H358, Calu-3, SNU-1327, and H1703) were stimulated with the EGF and treated with gefitinib and endocytosis inhibitors (phenylarsine oxide (PAO) and Filipin III). Growth inhibition and apoptosis were evaluated. Immunofluorescence, immunoprecipitation, and western blot assay were performed to investigate EGFR endocytosis and determine the signaling pathway. Xenograft mouse models were used to verify the combination effect of gefitinib and PAO in vivo. RESULTS: We confirmed the differences in EGFR endocytosis according to gefitinib response in wild-type EGFR NSCLC cell lines. EGFR in gefitinib-sensitive and -refractory cell lines tended to internalize through distinct routes, caveolin-mediated endocytosis (CVE), and clathrin-mediated endocytosis (CME). Interestingly, while suppressing CME and CVE did not affect cell survival in sensitive cell lines significantly, CME inhibition combined with gefitinib treatment decreased cell survival and induced apoptosis in gefitinib-refractory cell lines. In addition, blocking CME in the refractory cell lines led to downregulate of p-STAT3 and inhibit nuclear localization of STAT3 in vivo, combination treatment with gefitinib and a CME inhibitor resulted in tumor regression accompanying apoptosis in xenograft mouse models. CONCLUSION: Clathrin-mediated EGFR endocytosis contribute primary resistance of gefitinib treatment and CME inhibition combined with gefitinib could be an option in treatment of wild-type EGFR NSCLC.

Tumor Suppressor miR-584-5p Inhibits Migration and Invasion in Smoking Related Non-Small Cell Lung Cancer Cells by Targeting YKT6.

Cigarette smoke (CS) affects the expression of microRNAs (miRNAs), which are important regulators of gene expression by inducing DNA methylation. However, the effects of smoking on miRNA expression have not been fully elucidated in smoking-related lung carcinogenesis. Therefore, in this study, to investigate the change of miRNA expression pattern and to identify tumor suppressor miRNAs by smoking in lung carcinogenesis, we used lung carcinogenesis model cell lines that, derived from a murine xenograft model with human bronchial epithelial cells (BEAS-2B), exposed CS or not. The microarray analysis revealed that miR-584-5p expression was downregulated with cancer progression in lung carcinogenesis model cell lines. We confirmed by pyrosequencing that the methylation level of the miR-584-5p promoter increased with cancer progression. In vitro and in vivo experiments showed that miR-584-5p suppressed migration and invasion in non-small cell lung cancer (NSCLC) cells by targeting YKT6. Furthermore, we showed that high level of YKT6 was associated with a poor survival rate in NSCLC patients with a history of smoking. These results suggest that miR-584-5p acts as a tumor suppressor and is a potential molecular biomarker for smoking-related NSCLC.

Clinical Application of Targeted Deep Sequencing in Metastatic Colorectal Cancer Patients: Actionable Genomic Alteration in K-MASTER Project.

PURPOSE: Next-generation sequencing (NGS) can facilitate precision medicine approaches in metastatic colorectal cancer (mCRC) patients. We investigated the molecular profiling of Korean mCRC patients under the K-MASTER project which was initiated in June 2017 as a nationwide precision medicine oncology clinical trial platform which used NGS assay to screen actionable mutations. MATERIALS AND METHODS: As of 22 January 2020, total of 994 mCRC patients were registered in K-MASTER project. Targeted sequencing was performed using three platforms which were composed of the K-MASTER cancer panel v1.1 and the SNUH FIRST Cancer Panel v3.01. If tumor tissue was not available, cell-free DNA was extracted and the targeted sequencing was performed by Axen Cancer Panel as a liquid biopsy. RESULTS: In 994 mCRC patients, we found 1,564 clinically meaningful pathogenic variants which mutated in 71 genes. Anti-EGFR therapy candidates were 467 patients (47.0%) and BRAF V600E mutation (n=47, 4.7%), deficient mismatch repair/microsatellite instability-high (n=15, 1.5%), HER2 amplifications (n=10, 1.0%) could be incorporated with recently approved drugs. The patients with high tumor mutation burden (n=101, 12.7%) and DNA damaging response and repair defect pathway alteration (n=42, 4.2%) could be enrolled clinical trials with immune checkpoint inhibitors. There were more colorectal cancer molecular alterations such as PIK3CA, KRAS G12C, atypical BRAF, and HER2 mutations and even rarer but actionable genes that approved or ongoing clinical trials in other solid tumors. CONCLUSION: K-MASTER project provides an intriguing background to investigate new clinical trials with biomarkers and give therapeutic opportunity for mCRC patients.

The Clinical Significance of RAS, PIK3CA, and PTEN Mutations in Non-Small Cell Lung Cancer Using Cell-Free DNA.

Mutations in the EGFR gene downstream signaling pathways may cause receptor-independent pathway activation, making tumors unresponsive to EGFR inhibitors. However, the clinical significance of RAS, PIK3CA or PTEN mutations in NSCLC is unclear. In this study, patients who were initially diagnosed with NSCLC or experienced recurrence after surgical resection were enrolled, and blood samples was collected. Ultra-deep sequencing analysis of cfDNA using Ion AmpliSeq Cancer Hotspot Panel v2 with Proton platforms was conducted. RAS/PIK3CA/PTEN mutations were frequently detected in cfDNA in stage IV NSCLC (58.1%), and a high proportion of the patients (47.8%) with mutations had bone metastases at diagnosis. The frequency of RAS/PIK3CA/PTEN mutations in patients with activating EGFR mutation was 61.7%. The median PFS for EGFR-TKIs was 15.1 months in patients without RAS/PIK3CA/PTEN mutations, and 19.9 months in patients with mutations (p = 0.549). For patients with activating EGFR mutations, the overall survival was longer in patients without RAS/PIK3CA/PTEN mutations (53.8 months vs. 27.4 months). For the multivariate analysis, RAS/PIK3CA/PTEN mutations were independent predictors of poor prognosis in patients with activating EGFR mutations. In conclusion, RAS, PIK3CA and PTEN mutations do not hamper EGFR-TKI treatment outcome; however, they predict a poor OS when activating EGFR mutations coexist.

Clinical Implication of Concordant or Discordant Genomic Profiling between Primary and Matched Metastatic Tissues in Patients with Colorectal Cancer.

PURPOSE: The purpose of this study was to identify the concordant or discordant genomic profiling between primary and matched metastatic tumors in patients with colorectal cancer (CRC) and to explore the clinical implication. MATERIALS AND METHODS: Surgical samples of primary and matched metastatic tissues from 158 patients (335 samples) with CRC at Korea University Anam Hospital were evaluated using the Ion AmpliSeq Cancer Hotspot Panel. We compared genetic variants and classified them as concordant, primary-specific, and metastasis-specific variants. We used a combination of principal components analysis and clustering to find genomic groups. Kaplan-Meier curves were used to appraise survival between genomic groups. We used machine learning to confirm the correlation between genetic variants and metastatic sites. RESULTS: A total of 282 types of deleterious non-synonymous variants were selected for analysis. Of a total of 897 variants, an average of 40% was discordant. Three genomic groups were yielded based on the genomic discrepancy patterns. Overall survival differed significantly between the genomic groups. The poorest group had the highest proportion of concordant KRAS G12V and additional metastasis-specific SMAD4. Correlation analysis between genetic variants and metastatic sites suggested that concordant KRAS mutations would have more disseminated metastases. CONCLUSION: Driver gene mutations were mostly concordant; however, discordant or metastasis-specific mutations were present. Clinically, the concordant driver genetic changes with additional metastasis-specific variants can predict poor prognosis for patients with CRC.

Single-nucleotide polymorphisms in the promoter of the CDK5 gene and lung cancer risk in a Korean population.

Cyclin-dependent kinase 5 (CDK5), a proline-directed serine/threonine kinase, which was originally known for its regulatory role in neuronal activities, has recently been suggested to play a role in extraneuronal activities. For example, a recent study detected overexpression of the CDK5 gene in non-small-cell lung cancer. Therefore, in order to explore the association of the CDK5 gene with lung cancer risk in a Korean population, the genotypes of the CDK5 promoter region were determined in 407 lung cancer patients and 402 normal participants. The result showed that the -904 G>A genotype affected susceptibility to lung cancer risk (odd ratios (OR)=1.53, 95% confidence interval (CI)=1.02-2.32). Furthermore, subsequent haplotype analysis of three single-nucleotide polymorphism (SNP) regions suggested that the A-G-C haplotype was associated with a higher overall risk of lung cancer (OR=1.59, 95% CI=1.16-2.18). These results suggest that CDK5 promoter polymorphisms contribute to the genetic susceptibility to lung cancer in the Korean population.

Clinical implications of circulating cell-free DNA quantification and metabolic tumor burden in advanced non-small cell lung cancer.

OBJECTIVES: This study unravels the significance of cell-free DNA (cfDNA) quantification as a promising measure of the biological behavior/aggressiveness of tumors. Metabolic tumor volume (MTV) and total lesion glycolysis (TLG) measured by positron emission tomography/computed tomography scan enable a precise assessment of metabolic tumor burden. However, their clinical implications in identifying patients who need more aggressive treatment in advanced non-small cell lung cancer (NSCLC) are not fully understood. MATERIALS AND METHODS: In the current prospective trial, we analyzed 101 newly diagnosed advanced NSCLC (stage III-IV) patients with measurable baseline MTV, TLG, and cfDNA quantification. The best cut-offs for cfDNA levels, MTV, and TLG to predict progression-free survival and overall survival were determined using X-tile analysis. RESULTS: There were significant positive correlations between cfDNA and MTV (r = 0.488, p < 0.001) and between cfDNA and TLG (r = 0.554, p < 0.001). High-cfDNA levels and high-MTV/TLG negatively correlated with overall survival (OS) (all p < 0.001). Patients with high-MTV showed similar median OS irrespective of their cfDNA levels (low-cfDNA vs. high-cfDNA=9.2 vs 6.6 months; p > 0.05). However, patients with low-MTV and low-cfDNA levels showed longer OS than those with low-MTV and high-cfDNA levels (low-cfDNA vs. high-cfDNA=49.3 vs 11.5 months; p < 0.001). The patient group with low-TLG also showed similar trends. The cfDNA level was an independent prognostic factor for OS by Cox-proportional hazard analysis. CONCLUSION: Although the patients with high metabolic tumor burden had a poor prognosis, regardless of the biological behavior/aggressiveness of the tumor, patients with low metabolic tumor burden and high cfDNA levels showed a poor prognosis. Taken together, this study indicates a stronger prognostic value of baseline cfDNA levels in identifying patients with advanced NSCLC and personalizing their treatment strategies for better survival.

Putative association of the single nucleotide polymorphisms in RASSF1A promoter with Korean lung cancer.

SUMMARY: The RASSF1 gene, a putative tumor suppressor gene located on human chromosome 3p21, has attracted a great deal of attention because of frequent allelic loss and gene silencing via promoter hypermethylation in a variety of human malignancies. To evaluate the role of RASSF1A gene in lung cancer risk, genotypes of the RASSF1A promoter region (-710 C>T and -392T>C) were determined in 410 lung cancer patients and 410 normal subjects. Furthermore, to examine potential effects of the common haplotypes (C-C, T-T and C-T haplotypes) on RASSF1A transcription, luciferase reporter assays were performed in H2009 and H358 non-small cell lung cancer (NSCLC) cell lines. We found that ht2 C-T haplotype was associated with susceptibility to the risk of lung cancer in dominant (odds ratio (OR): 0.69; 95% CI: 0.46-0.99) model. In particular, we found that C-T haplotype showed a decreased risk of lung cancer in males (codominant OR: 0.59; 95% CI: 0.38-0.93 and dominant OR: 0.58; 95% CI: 0.35-0.96) and in smokers (codominant OR: 0.58; 95% CI: 0.36-0.93 and dominant OR: 0.56; 95% CI: 0.33-0.96). Interestingly, C-T haplotype induced transcriptional activity by 50-60% compared with other haplotypes in NSCLC cell lines. These results suggest that RASSF1A promoter polymorphisms affect RASSF1A expression, further contributing to the genetic susceptibility to lung cancer.

Single nucleotide polymorphisms of IGFBP-3 gene and lung cancer risk in a Korean population.

Insulin-like growth factor binding protein-3 (IGFBP-3) is a putative tumor suppressor and inhibits the mitogenic and antiapoptotic activity of insulin-like growth factor (IGF) by blocking the binding to its receptors or by IGF-independent manner. Epidemiological studies have suggested that serum level of IGFBP-3 is associated with lung cancer risk. The present study was conducted to evaluate the association between single nucleotide polymorphisms (SNPs) of the IGFBP-3 gene and susceptibility to lung cancer and the effect of the SNPs on the serum levels of IGFBP-3, total IGF-I and free IGF-I in a Korean population. After a preliminary study for polymorphism screening of the promoter region of the IGFBP-3 gene in randomly selected 41 lung cancer patients, two polymorphisms (-1590 C>A; -202 A>C) were identified with PCR-based restriction fragment length polymorphism (PCR-RFLP) and SNaPshot primer extension assay in 415 Korean lung cancer patients and 415 matched normal controls. Although the genotype and allele frequency distribution of each SNP did not differ significantly between cases and controls in the single-locus analysis, we found that the polymorphisms of -1590A and -202C were associated with increased risk for lung cancer in females (-1590 C>A; adjusted OR=2.11, 95% CI=1.08-4.12, -202 A>C; adjusted OR=1.96, 95% CI=1.02-3.75, respectively) and never-smokers (-1590 C>A; adjusted OR=2.06, 95% CI=1.12-3.78, -202 A>C; adjusted OR=1.99, 95% CI=1.10-3.62, respectively) in a dominant model after stratification for gender and smoking history. Haplotype analysis showed that carriers of A-C had significantly higher risk for lung cancer in females (dominant aOR=2.05, 95% CI=1.14-3.68) and in never-smokers (codominant aOR=1.71, 95% CI=1.11-2.64 and dominant aOR=1.99, 95% CI=1.17-3.40). Functional analysis in H1703 cell line using DNA fragments containing A-C haplotype of the promoter region showed significantly decreased transcriptional activity. Furthermore, there was a negative correlation between the number of polymorphic alleles in -1590/-202 loci and serum levels of IGFBP-3 in lung cancer patients, but it was not statistically significant in the test for linear trend. These results suggest that IGFBP-3 promoter polymorphisms of -1590 C>A and -202 A>C might be a genetic risk factor for lung cancer by means of decreased IGFBP-3 expression among females or never-smoking Koreans.

Isolation of spheroid-forming single cells from gastric cancer cell lines: enrichment of cancer stem-like cells.

Isolation of spheroid-forming cells is important to investigate cancer stem cell (CSC) characteristics. However, conventional tumor spheroid culture methods have not proven suitable because the aggregated spheroids generally maintain their original heterogeneity and harbor multiple cells with various characteristics. Here we cultured spheroids using a polydimethylsiloxane microwell-based method and a limiting dilution protocol. We then isolated and enriched for CSCs that formed single cell-derived spheroids from gastric cancer cell lines. Cells from the microwell demonstrated higher self-renewal, increased expression of stem cell markers and resistance to apoptosis compared with spheroid cells made by the traditional method. This novel approach allows efficient cancer stem cell isolation and represents a step forward in cancer stem cell studies.

Quantification of circulating cell-free DNA to predict patient survival in non-small-cell lung cancer.

We used computed tomography (CT) to explore the prognostic value of cell-free (cf) DNA quantification and its predictive efficacy over time after chemotherapy in non-small-cell lung cancer (NSCLC) patients. In total, 177 NSCLC patients were enrolled in a prospective biomarker trial. Consecutive paired blood collection was performed to determine cfDNA concentrations at baseline CT and throughout serial follow-ups. The best cfDNA cut-off value to predict progression-free and overall survival was determined using X-tile analysis. Among 112 chemo-naive patients with stage IV adenocarcinoma, 43 were available for follow-up analysis. Cox regression multivariate analysis indicated that a high cfDNA concentration was an independent negative prognostic factor for progression-free survival (hazard ratio: 2.60; 95% confidence interval: 1.65-4.10; p = 0.008) and overall survival (hazard ratio: 2.63; 95% confidence interval: 1.66-4.17; p < 0.001). However, cfDNA concentration changes during treatment did not correlate with radiological CT responses at first follow-up or best response. No pattern was noted in the percent change in the cfDNA concentration from baseline or subsequently measured level to progression. The serum cfDNA concentration is thus associated with NSCLC patient prognosis, but does not appear to be a clinically valid marker for tumor responses.

Detection of somatic variants and EGFR mutations in cell-free DNA from non-small cell lung cancer patients by ultra-deep sequencing using the ion ampliseq cancer hotspot panel and droplet digital polymerase chain reaction.

Highly sensitive genotyping assays can detect mutations in cell-free DNA (cfDNA) from cancer patients, reflecting the biology of each patient's cancer. Because circulating tumor DNA comprises a small, variable fraction of DNA circulating in the blood, sensitive parallel multiplexing tests are required to determine mutation profiles. We prospectively examined the clinical utility of ultra-deep sequencing analysis of cfDNA from 126 non-small cell lung cancer (NSCLC) patients using the Ion AmpliSeq Cancer Hotspot Panel v2 (ICP) and validated these findings with droplet digital polymerase chain reaction (ddPCR). ICP results were compared with tumor tissue genotyping (TTG) results and clinical outcomes. A total of 853 variants were detected, with a median of four variants per patient. Overall concordance of ICP and TTG analyses was 90% for EGFR exon 19 deletion and 88% for the L858R mutation. Of 34 patients with a well-defined EGFR activating mutation defined based on the results of ICP and TTG, 31 (81.6%) showed long-term disease control with EGFR TKI treatment. Of 56 patients treated with an EGFR tyrosine kinase inhibitor (TKI), the presence of the de novo T790M mutation was confirmed in 28 (50%). Presence of this de novo mutation did not have a negative effect on EGFR TKI treatment. Ultra-deep sequencing analysis of cfDNA using ICP combined with confirmatory ddPCR was effective at defining driver genetic changes in NSCLC patients. Comprehensive analysis of tumor DNA and cfDNA can increase the specificity of molecular diagnosis, which could translate into tailored treatment.

Can Serum be Used for Analyzing the KRAS Mutation Status in Patients with Advanced Colorectal Cancer?

PURPOSE: KRAS mutations have been used widely as prognostic or predictive marker in patients with advanced colorectal cancer (CRC). However, it may be difficult to obtain a tumor tissue for analyzing the status of KRAS mutation in large proportion of patients with advanced disease. MATERIALS AND METHODS: We obtained pairs of tumor and serum samples from 65 patients with advanced CRC, between March 2008 and July 2011. KRAS mutation status from the tumor samples was analyzed by genomic polymerase chain reaction and direct sequence, and KRAS mutation status from the serum samples was determined by a genomic polymerase chain reaction-restriction fragment length polymorphism assay. RESULTS: KRAS mutations were detected in the serum samples of 26 patients and in the tumor samples of 31 patients. KRAS mutation status in the serum and tumor samples was consistent in 44 of the 65 pairs (67.7%). There was a significant correlation between the mutations detected in the serum sample and the mutations detected in the matched tumor sample (correlation index, 0.35; p < 0.004). Twenty-two of the 57 patients (38.5%) received anti-epidermal growth factor receptor therapy as any line therapy. There was no significant difference in the overall survival (OS) in accordance to the status of KRAS mutations in both the serum and tumor samples (p > 0.05). In a multivariate analysis, liver metastasis and no cytoreductive operation were independent prognostic factors for decreased OS. CONCLUSION: The serum sample might alternatively be used when it is difficult to obtain tumor tissues for analyzing the status of KRAS mutation in patients with advanced CRC.

EGFR endocytosis is a novel therapeutic target in lung cancer with wild-type EGFR.

Oncogenic alterations of epidermal growth factor receptor (EGFR) signaling are frequently observed in lung cancer patients with worse differentiation and poor prognosis. However, the therapeutic efficacy of EGFR-tyrosine kinase inhibitors (TKIs) is currently limited in selected patients with EGFR mutations. Therefore, in this study, we investigated the potential molecular mechanism that contributes to cell viability and the response of gefitinib, one of the EGFR-TKIs, in lung cancer models with wide-type EGFR (wtEGFR). Interestingly, we found that EGF-induced EGFR endocytosis is existed differently between gefitinib-sensitive and -insensitive lung cancer cell lines. Suppressing EGFR endocytos decreased cell viability and increased apoptotic cell death in gefitinib-insensitive lung cancer with wtEGFR in vitro and in vivo. In addition, we found that Rab25 was differentially expressed in between gefitinib-sensitive and -insensitive lung cancer cells. Rab25 knockdown caused the changed EGFR endocytosis and reverted the gefitinib response in gefitinib-sensitive lung cancer with wtEGFR in vitro and in vivo. Taken together, our findings suggest a novel insight that EGFR endocytosis is a rational therapeutic target in lung cancer with wtEGFR, in which the combined efficacy with gefitinib is expected. Furthermore, we demonstrated that Rab25 plays an important role in EGFR endocytosis and gefitinib therapy.